The present invention relates to a spinning rotor for an open-end spinning unit of the type having an intake portion whose cross section widens in the direction toward the fiber collecting trough and presents a stepped, or outwardly projecting, section which merges into and defines one boundary of the fiber collecting trough and which increases the diameter of the rotor. The side of the fiber collecting trough which is opposite the stepped section is defined by the bottom surface of the spinning rotor.
In a rotor of this type, the radially outermost end of the stepped section defines the maximum diameter of the fiber collecting trough, and the trough portion following that outermost end, i.e. between that end and the rotor bottom surface, has, at least in the area of transition between the trough and the spinning rotor bottom surface, a smaller diameter. In addition, the axial distance between the projection of the bottom surface and the radial innermost end of the stepped section is between 1/16 and 1/6 of the largest diameter of the fiber collecting trough. This axial distance is measured from the intersection of the projection of the rotor bottom surface on a cylinder centered on the rotor axis and passing through the radially outermost end of the stepped section surface. Such a structure is disclosed in commonly assigned copending U.S. application Ser. No. 700,125, filed by Rolf Neubert and Rolf Wehling on June 28th, 1976.
A spinning structure is known in which the fiber collecting trough has a cross section which becomes wider in the direction toward the bottom surface of the spinning rotor. In the area of the bottom surface of the spinning rotor the fiber collecting trough is limited by a further stepped section which constitutes part of the spinning rotor bottom surface, and in the latter stepped section there are provided air bores whose longitudinal axes are perpendicular to the rotor axis.
The drawback of this known spinning structure is, in particular, that the widening cross section of the fiber collecting trough in the direction toward the bottom surface of the spinning rotor, facilitates depositing of impurities in the fiber collecting trough and, moreover, no means are provided to permit removal of impurities from the fiber collecting trough. The interior entrance cross sections of the air bores are disposed at a significantly smaller diameter, i.e. closer to the rotor axis, than is the fiber collecting trough and the section before it. Consequently, they are not intended for cleaning of the fiber collecting trough and are not suited for this purpose.
It has been proposed to promote cleaning of the spinning rotors of open-end spinning machines by providing protrusions on the fiber collecting trough, at least on one side thereof, which protrusions are separated from one another by gaps.
According to another known arrangement, air bores are provided outside of the fiber collecting trough in the intake portion, or in the spinning rotor bottom surface opposite the intake portion.
In the units which have protrusions, it is not possible to dependably prevent fibers from being ejected together with the impurities to be removed.
The arrangements which have air bores in the intake portion or in the bottom surface of the spinning rotor have the drawback that the available air bores are hardly suitable for the removal of impurities from the fiber collecting trough, and thus from the spinning rotor. Moreover, there exists the danger, in these arrangements, that the air bores may become clogged, particularly with fiber material, during operation.